This invention relates generally to the production of gluten, and in particular to an automatic system which combines wheat flour and water to produce dough and then extracts therefrom the gluten component, all of these actions taking place continuously.
The present invention represents a step beyond the automatic dough-producing systems disclosed in my copending applications in which flour and a dough-producing solution are mixed in a mixer stage to form a paste which is then developed into dough in a developer stage, for in the present invention the dough is supplied to a separator stage in which the gluten is extracted therefrom.
Because of the ever increasing consumption of fabricated and so-called "junk" foods that are notoriously deficient in nutritional value, there has been a concomitant growth in the demand for vegetable proteins with special functional properties. Wheat gluten which possesses a high protein content and unique structural and adhesive properties is the water insoluble complex protein fraction in wheat flours. In its freshly extracted wet state it is known as gum gluten and when thereafter dried it becomes a free-flowing powder of high protein content and bland taste. When gluten powder is re-hydrated, it regains its original characteristics.
Wheat gluten is now widely used to fortify breakfast cereals and it is also valuable to bakers, for it acts to strengthen dough, to retain gas and to control expansion, these characteristics resulting in uniformly-shaped baked products. And because gluten absorbs about twice its weight in water, its capacity for holding water gives rise to an increased yield and extended shelf life in many food systems. The useful properties of gluten and its many advantages are set forth in greater detail in the booklet "Wheat Gluten--A Natural Protein for the Future--Today" published in 1981 by the International Wheat Gluten Association--Shawnee, Kans.
The basic procedure for gluten manufacture involves mixing flour with a dough-producing solution to produce a paste which is developed to form dough, the washing of the dough to remove as much of the starch and other soluble flow components as possible, the drying of the gluten to a low moisture content, and finally the reduction of the dried gluten to powder form.
Various techniques are known to separate gluten from starch. Perhaps the oldest is the "Martin process" in which the dough, after hydration, is rolled between fluted rolls and kneaded in a trough with reciprocating rolls under water at high pressure. This action washes away the starch and leaves a mass of gluten.
In the "batter process" developed by the U.S. Department of Agriculture, a soft coherent mass of dough is mechanically broken up in the presence of additional water to yield suspended curds of gluten with the starch removed. The curds are recovered on a gyrating screen through which the starch milk passes. The "Fesca" or direct centrifiguration process results in a well dispersed slurry of flour without gluten development. The starch can be removed from suspension by centrifiguration while the protein remains suspended.
The more recent "Alfa-Laval" gluten extraction process is regarded in an article appearing in the publication "Milling and Baking News" of July 4, 1978 as offering advantages over earlier extraction techniques. This process converts whole wheat into a coarse flour which is mixed with water to form a thick batter. The batter is then homogenized in a disc type unit which discharges a slurry of starch, protein and other flour components. This step is followed by centrifiguration which fractionates the flour into prime starch, B-starch, vital gluten and dried solubles.
The ability to extract insoluble gluten from dough by means of water which dissolves the starch and other soluble components depends on the extent to which the dough is-exposed to the water wash. Thus if the dough is in large mass and the surface of this mass is subjected to water, only the surface region of the mass will have its soluble components removed and the body of the mass will be largely unaffected by the water. While in prior methods, the mass of dough is broken down into smaller globules or pieces, what is still lacking is intimate washing contact between the water and virtually all areas of the dough; hence the resultant gluten is not entirely free of starch or other non-protein components.
Another factor which comes into play is the entrapment of the starch in the gluten. This occurs in the course of development of the paste, for a point may be reached in development where the starch becomes encapsulated in the gluten gum and is thereby insulated from the water later used to dissolve the starch, thereby degrading the quality of the gluten produced by the system.